Cheap Guitar Amps

Guitar Tube Amps

Early amplifiers were made for radios and switchboards and PA systems, and were not really made for guitar. But things change.

In the 1930s, early amplifiers were initially driven by batteries, but by the 1940s (and the Rural Farm Electricification Act) electricity was widely available, and so it was natural to change power to normal house current.

In the 30s and 40s, hawaiian music experienced a ongoing surge of popularity, and the Hawaiian guitar (a type of lap steel guitar) helped to make the concept of an amplified electric guitar a reality in popular music.

Early amplifiers were driven by vacuum tubes. A vacuum to tube is called an amplifier but it's really a controller. A small voltage in, let us say the middle of the tube, upon a metal plate, causes a larger electrical signal flowing for example from one end to the other to be increased or decreased.

The small current creating a charge upon the plate is now hindering or permitting the passage of the larger current. In this way the small fluctuating signal controls the large signal and causes it to fluctuate, and now we have a larger fluctuating signal. It's the same signal, but now the signal has become a much larger signal. So the shape or wave of the signal has been transferred from the small voltage to the large voltage, and therefore the signal itself has been made big, or amplified.

Vacuum tubes are called vacuum tubes because the air is taken out. The reason for taking the air out is because if you don't, then the voltage making the plates inside glow red would simply cause them to oxidize, or burn up. In a vacuum, no oxygen. No oxygen no burning up. The plate can glow red, becoming hot, and yet continues to function.

The vacuum tube was the basis for pretty much all audio circuitry for many years.

And Then ... Rock and Roll

In the 1960s, about the time of the so-called British Invasion in rock 'n roll music, guitar players learned that by overdriving the input signals of their amplifiers they could create a distorted sound. And they liked it. Overdrive and distortion became part of the sound of rock 'n roll and blues.

In modern times guitar amplifiers are primarily either solid-state or "tube type." Solid-state amps can be less expensive, and actually track more accurately, are more reliable, are more durable, weigh less, they have less heat problems, and they do not require the ongoing maintenance of replacing vacuum tubes which wear out.

But tube type amps have a sound that we like.

There seems to be several reasons why we often find the sound of a tube type amplifier to be more pleasing:

Soft Clipping is a Sweet Sound

As the input part of the tube becomes overloaded, it begins to distort. What that means is the wavelike alternation of electricity approaches and hits the limit of what the tube can handle. So in effect the top or highest part of the wave and also the bottom or lowest part of the wave is, so to speak, hitting the ceiling and the floor, and being squared off because it can't go any higher or any lower.

Without going into the math of why this is true, it is a fact that when we add harmonics to a wave it tends to change the wave to a squared-off shape. In fact, the squared-off shape from adding harmonics to a sound wave and the squared-off shape from a vacuum tube hitting its upper and lower limits are essentially the same shape.

So when the vacuum tube signal gets squared off, our ears to hear it as a richer set of harmonics being added to the sound that was there before.

Hard and Soft Clipping

Now, solid-state amps can also be overdriven, and there too the sound way becomes squared off. However, a tube amp approaches this squaring-off state rather gradually, and this sounds pretty good. A solid-state amp hangs in thereuntil it suddenly hits the squared-off state like hitting a wall, and it sounds pretty crappy. It sort of screeches.

In other words, the squared-off state, or "clipping", of the tube type amp is a type of "soft clipping" which clips more and more gradually. This lets us dial-in just the amount of distortion -- or, to our ear, added harmonics -- that we want. For this reason, many guitarists prefer the sound of tube type amps.

(Sometimes the guitarist will use the tube sound in the first stage of an amp, the pre--amplifier, and then with that sweet sound use the more reliable and durable and inexpensive solid-state final amplification, because you don't usually need to overdrive in the later section of the amplifier. If you already have the sweet sound of the tube and you make it louder, then you have a loud sweet sound.)

Other Audio Advantages of Guitar Tube Amps

There are a couple of other reasons that engineers and guitarists will mention is a part of the preferable sound of a guitar tube amp.

For historical reasons, and for reasons of sound, early guitar amplifier design tended to have more powerful vacuum tubes and less powerful output transformers. There is an interplay between a vacuum tube and the output transformers. In some cases a surge in the signal going through the vacuum tube will cause a drop in the power inside the power transformer. This causes a different type of altered fidelity, but an alteration whose sound we generally enjoy.

Even and Odd Harmonics

When you consider the harmonics or overtones of a vibrating string or an electronic signal you will discover that even harmonics sound different than odd harmonics.

For example, if you took the first, third, fifth, and seventh harmonics of a vibrating string, and you had a way to hear only those harmonics, you will hear that it has a hollow or strange sound. An oboe instrument has a double reed, and a double reed tends to produce only the odd harmonics in the sound, and thus the oboe has a hollow and strange sound to our ears.

When you take only the even harmonics, we tend to hear that sound as being rich, fat, and full. It has been observed that guitar to amps, as they begin to distort, are adding primarily even harmonics. For this reason, we tend to hear the distortion of a guitar tube amp as being rich, fat, full, and pleasing.

Solid-state amps don't do that, and they don't sound sweet, rich, fat, nor pleasing when the signal is overdriven.

Vacuum Tube Production

The US military at one point obtained a Soviet satellite from the early days of space exploration. And our scientists were quite amazed, because when they examined it they discovered it was full of circuits and the circuits were built of thousands of tiny reliable vacuum tubes. (The USA had fully converted to transistorized circuits long since but the Soviets did not have that technology. The US had abandoned vacuum tube technology, but the Soviets had continued to develop it.)

Most vacuum tubes used in guitar tube amps today come from Russia and from China because of those countries had continued to develop and produce vacuum tubes when they had already become something of a scarce commodity in the USA.

Those Troublesome Guitar Tube Amps

Vacuum tubes are low-current and high-voltage devices, compared to transistors. The high voltages makes them run hot, which is one of the contributing factors to their lives being shorter than transistors. The tubes must be replaced now and then, and they generally last only one to three years. Tube amplifiers are more delicate, and they weigh more, and they cost more.

Why do we use them?

Because they sound so sweet.

Finding Guitar Tube Amps at Great Prices --

Online Discount Musician Stores

We've often heard these online stores reported as having great deals --

Your Local Music Store

Big chain stores like Guitar Center sometimes run sales. Be sure you know your amp, and audition it before buying. But remember, many smaller guitar stores, in order to get your business, will match online-discount pricing, and smaller guitar stores can often provide you superior customer service.

Amazon

Sometimes great values, sometimes not, depending upon the seller.

EBay

Frequently the price-value winner, especially if you’re willing to buy used. It’s hard to beat EBay. Just look at this huge selection of best-value guitar amps, instruments, and amp effects available right now –